Cryptology ePrint Archive: Report 2007/317

Improving Upon the TET Mode of Operation

Palash Sarkar

Abstract: Naor and Reingold had proposed the construction of a strong pseudo-random
permutation (SPRP) by using a layer of ECB encryption between two layers of
invertible block-wise universal hash functions. At Crypto 2007, Halevi presented
constructions of invertible block-wise universal hash functions and a new mode
of operation (called TET) based on them. In this paper, we present a new mode
of operation
called {\heh} using the Naor-Reingold approach. This is built using a new
construction of invertible block-wise universal hash function. The new
construction improves over Halevi's construction by removing restrictions on
the hashing key. This in turn, leads to {\heh} improving
over TET by allowing more efficient encryption and decryption of variable length
messages as well as supporting better key agility. For the important application
of disk encryption, we present a variant called {\hehfp} which has better
key agility than TET.